Currently, the local time setting of most in-vehicle clocks and clock radios need to be manually set each time, for example, the battery is disconnected, the vehicle enters into another time zone, or the local time is affected by changes to or from daylight savings time. The in-vehicle clocks need to be reset whenever the displayed time is out of synchronization with the local time setting. Several methods have been implemented to assist in setting of clocks and other time-sensitive modules in a vehicle to the local time.
One method in the last few years employs specialized radio receivers with clocks that use radio data system (RDS) technology. This technology allows radio broadcasters to silently deliver a 1,200 bits-per-second data stream on a subcarrier of a normal FM radio signal, with the data messaging typically modulated just above the stereo audio at 57 kHz. Information such as local radio time may be encoded on the FM subcarrier and transmitted from radio stations to specialized RDS receivers, which may periodically reset the car clock. It has been estimated that approximately 15 percent of the approximately 7,000 FM stations in the United States use RDS. Unfortunately, the time set by an RDS radio station is often dependent on the accuracy of a radio engineer's setting. Another minor problem has been differences between decoding displays of the European PTY (Program Type) decoding and the January 1998 US (January 1993 RBDS) decoding that U.S. radio stations typically use. FM radio sub-carrier time information used in determining local time requires additional software and hardware costs for an original equipment manufacturer (OEM) and is often not available on installed clock radios.
Another method for receiving local time in a vehicle uses Greenwich Mean Time (GMT) data broadcast from a global positioning system (GPS) and received by an in-vehicle GPS receiver. The time-stamp data, which cannot by itself provide local time, may use an algorithm that converts the Greenwich Mean Time (GMT) into local time. This algorithm, however, requires an additional source, such as a database of all geographical areas based on local coordinates and the time shifts of each geographical area with respect to GMT, to convert GMT into local time.
It is desirable, therefore, to provide a system and method that gives accurate local time to a vehicle and automatically synchronize an in-vehicle clock and other time-receiving devices with the local time, and to overcome the challenges and obstacles described above.